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Old 09-18-16, 09:26 AM   #2
jeff5may
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With most mini-split units, especially electronic expansion valve, inverter-driven compressor types, the outdoor unit is not much different (if at all) in the lower capacity ranges. When matched up with the smaller-capacity indoor units, the outdoor unit just runs slower throughout its useful range. This puts the outdoor unit in its high-efficiency mode and HSPF and EER values are heavenly. The main difference between outdoor units is how many indoor units can be plumbed into and operated off of one outdoor unit...at least up into the two-ton range.

Naturally, the price of a more capable unit will be more expensive than one that can only be rigged to one indoor unit. It would be wrong for the marketing professionals not to jack up the price considerably. In some cases, it is not much more expensive to buy two smaller single-zone units rather than one multi-zone unit of comparable maximum capacity. I am still wondering what a dual-capacity, variable-speed compressor really is on the inside...

The longer you wait, the more savings you are passing up...good deals come and go every day. Plus, installing stuff in the winter is cold and miserable. I would rather invest sweat equity than frostbite equity myself.

In general, mini-split units are more conservatively rated when compared to portable or window units as to raw BTU-moving ability, especially in heating mode. You testified to this difference yourself in another thread, comparing a window unit with a mini-split installed in a bedroom. In your case, I might only buy one unit of smaller capacity first and see if it fulfills the need sufficiently. After the first unit has changed the "comfort profile" of the home, it would be much easier to decide how big and where to install another one if necessary. I'm not you, though, and am much more tolerant of temperature swings in "fringe zone", less occupied areas, if it saves me some bucks.

From a capitalist perspective, the two smaller units would pay themselves back much sooner than the one larger unit, due to the energy efficiency advantage. The downside risk is also minimized, as there are now two points of possible failure rather than one. If one of the small outdoor units failed, not both, you still have half of the system running. Ask Xringer about that one. He thinks he's still in it for the money. The newer, digital microprocessor controlled units are inherently less resistant to power line dirt than the old-school "dumber" cap tube and TXV metered units. With higher ultimate efficiency comes the risk of control module failure.

Last edited by jeff5may; 09-18-16 at 10:33 AM.. Reason: elaborating on ideas
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